Method and Device for Addition of a Reducing Agent in an Exhaust Gas Line of an Internal Combustion Engine of a Motor Vehicle

ABSTRACT

The invention relates to a method and a device for the addition of a reducing agent in an exhaust gas line of an internal combustion engine of a motor vehicle, with at least one NO x  storage catalyst that is arranged in the exhaust gas line of the internal combustion engine, and with a metering device, by means of which a preset amount of a reducing agent is introduced into the exhaust gas line at preset times. The metering device is created from a stationary gas line connecting element that is made up of multiple parts at a defined position on the exhaust gas line and a connecting counter-element that can be connected in a detachable manner to this connecting element and that can be arranged independently of the exhaust gas line and motor vehicle, in particular removed from the motor vehicle, in such a way that the connecting counter-element, during service, in particular when the motor vehicle is parked and/or the internal combustion engine is idling, is connected to the exhaust gas line connecting element, and then, for purposes of regeneration of at least one NO x  storage catalyst for a preset time, a preset amount of reducing agent is introduced into the exhaust gas line. After the regeneration, the connecting counter-element is again detached from the exhaust gas line connecting element and stored at a preset location.

The invention relates to a method for the addition of a reducing agentin an exhaust gas line of an internal combustion engine of a motorvehicle.

BACKGROUND OF THE INVENTION

It is generally known that in NO_(x) storage catalysts, as service lifeincreases, NO_(x) regeneration capacity is reduced by the sulfurcomponents that are contained in the fuel or motor oil and that aredeposited in the NO_(x) storage catalyst. To counteract such a sulfurcontamination, various regeneration measures are already known forNO_(x) storage catalysts. For example, such a desulfurization of anNO_(x) storage catalyst can be achieved by traveling at high loads andhigh catalyst temperatures, which represents a so-called passiveregeneration. Alternatively to this, a desulfurization can also,however, be actively carried out by an operating method of the internalcombustion engine, by which the NO_(x) storage catalyst temperature isincreased in connection with an at least temporary exhaust gasenrichment, and reducing agent from the combustion engine is provided atthe same time by the combustion under lean-air conditions. The currentlycommon sulfur contents in the fuel of 10 to 50 ppm make it necessary todesulfurize the NO_(x) storage catalyst in order to meet the applicableexhaust gas standard approximately every 500 to 5,000 km. All such knownactive desulfurization methods for NO_(x) storage catalysts are based onproviding elevated exhaust gas temperatures of over 550° C. inconnection with a rich exhaust gas composition.

From DE 102 23 595 A1, moreover, a method is known for operating a motorvehicle with an NO_(x) storage catalyst, in which in connection with anextensive availability of low-sulfur or sulfur-free fuels, the value ofa state variable that characterizes a degree of sulfur contamination ofthe NO_(x) storage catalyst is first determined. As a state variable,the NO_(x) storage activity of the catalyst or the amount of NO_(x) thatcan be stored in the catalyst during a lean phase can be selected here.In addition, as a state variable, the amount of sulfur that is stored inthe catalyst during a preset time interval can also be selected. Inaddition, other variables can be the timing and duration of a release ofa lean operating phase of the internal combustion engine that aredetermined based on the amount of NO_(x) that can be stored in thecatalyst during a lean phase, and the release period of the leanoperating phase is selected as a state variable.

Based on the thus determined value of the state variable, an adjustmentof the internal combustion engine in the operating phase is then carriedout with a substoichiometric fuel-air ratio, the degree of efficiency ofthe internal combustion engine at any operating point between 50 km/hand 100 km/h being at most 3% worse than the same operating pointwithout the generated state signal, in particular at an operating pointthat corresponds to steady, straight and level travel at an outsidetemperature of 20°.

In addition, a method for reactivating a nitrogen oxide storagecatalyst, which has basic strontium or barium compounds on a carriermaterial that contains cerium oxide and, moreover, contains, with thecarrier material, strontium and/or barium compounds that are formed bythermal aging, is known from DE 10 2005 034 344 A1. For regeneration,the compounds of strontium and/or barium are decomposed with the carriermaterial by treatment with a gas mixture that contains nitrogen dioxide,water vapor and optionally carbon dioxide at temperatures of between300° and 500° C. An optimized regeneration of a nitrogen oxide storagecatalyst is to be achieved therefrom.

The object of this invention is to make available a method and a devicefor the addition of a reducing agent in an exhaust gas line of aninternal combustion engine of a motor vehicle, by means of which, inparticular in connection with low-sulfur fuels, a reliable and fail-saferegeneration of an NO_(x) storage catalyst of an exhaust gas line of aninternal combustion engine that is optimized in the event ofregeneration is possible.

SUMMARY OF THE INVENTION

According to the invention, a metering device is provided, by means ofwhich at preset times, a preset amount of a reducing agent can beintroduced into an exhaust gas line of an internal combustion engine ofa motor vehicle, to create a stationary gas line connecting element thatis made up of multiple parts at a defined position on the exhaust gasline and a connecting counter-element that can be connected in adetachable manner to this connecting element and that can be arrangedindependently of the exhaust gas line and motor vehicle and that can bearranged in particular removed from the motor vehicle. With such amulti-part design of the metering device, for service, the separate,connecting counter-element that is not carried along can preferably beconnected to the exhaust gas line connecting element if the motorvehicle is parked and/or the internal combustion engine is idling, andthen, for purposes of regeneration of at least one NO_(x) storagecatalyst for a preset time, a preset amount of reducing agent at apreset temperature can be introduced into the exhaust gas line. Aftercompletion of the regeneration, the connecting counter-element can againbe detached from the exhaust gas line connecting element and secured atthe site provided for this purpose.

This solution according to the invention is advantageous in particularin such internal combustion engines that are operated with a fuel whosesulfur content is less than or equal to 30 ppm, in particular less thanor equal to 10 ppm. Also, the reducing agent is preferably a mixture ofsubstances, with a sulfur content of less than or equal to 30 ppm, inparticular less than or equal to 10 ppm.

With such a solution according to the invention, targeteddesulfurization can be performed, namely independently of a streetoperation of a motor vehicle, in particular in connection withlow-sulfur fuels during servicing of the motor vehicle at an auto repairshop or at a service facility. Thus, the often difficult and emergencyservicing of engine electronics during the operation of a motor vehicleas well as other measures to be scheduled can be performed without thedriver being aware of them and will therefore also not impair thedriving comfort of the motor vehicle. Moreover, as a result, secondaryemissions as well as changes in combustion noise can be reliablyprevented.

According to another preferred configuration, the connectingcounter-element can be a component of a stationary or mobiledesulfurization device that is arranged at a service facility or autorepair shop. Thus, e.g., service sites can be set up at a servicefacility, by means of which the desulfurization and thus theregeneration of existing NO_(x) storage catalysts can easily beperformed during service.

The connecting counter-element and the exhaust gas line connectingelement can especially preferably be connected by means of aquick-release fastener. This quick-release fastener can be designedespecially simply to be sealed, in particular gas-tight and/orfluid-tight.

Moreover, the desulfurization device can preferably be designed with areducing agent reservoir for a reducing agent, as well as also a controland regulating device for defined charging of the exhaust gas line withreducing agent. Thus, a reliable and fail-safe addition of reducingagent during service is possible.

According to another actual configuration, the desulfurization devicehas a line connection, in particular a hose line connection, between thereducing agent reservoir and the connecting counter-element, whereby thecontrol and/or regulating device is then coupled or integratedindirectly or preferably directly into the hose line connection in thearea between the connecting counter-element and the reducing agentreservoir.

The desulfurization device can also have a heating device, by means ofwhich the reducing agent can be heated to a preset temperature. Thus, itis particularly easily ensured that the regeneration can also actuallybe performed effectively at the necessary temperatures.

According to an actual configuration, the exhaust gas line connectingelement can be arranged in the exhaust gas line in the area between adiesel particle filter and an NO_(x) storage catalyst, i.e., it canthus, according to a general idea, be arranged in front of at least oneNO_(x) storage catalyst in the direction of flow.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a diagram of a desulfurization system embodying the presentinvention connected to an exhaust gas system of a motor vehicle.

The

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The single figure shows diagrammatically a design of an exhaust gassystem of a motor vehicle with an internal combustion engine 1, to whichan exhaust gas line 2 is connected, in which, seen in the flow directionof the exhaust gas stream, an oxidation catalyst 3, a diesel particlefilter 4, an NO_(x) storage catalyst 5, a locking catalyst 6 as well asa noise damper 7 are integrated. In this case, the catalysts or othercomponents can have a conventional design and are not explained in moredetail below.

In the area between the diesel particle filter 4 and the NO_(x) storagecatalyst 5, a connecting point 8 for reducing agents during service isprovided here. At this connecting point 8, a metering device 9, which ismade up of multiple parts from a stationary, gas line-side gas lineconnecting element 9 a and a connecting counter-element 9 b that can beconnected detachably to the latter, is provided. As this is depictedonly diagrammatically in FIG. 1, the two components 9 a, 9 b arepreferably designed here in the form of a quick-coupling connection, sothat a tight connection of the two components 9 a, 9 b can be carriedout in a quick and reliable as well as fail-safe way. The same appliesanalogously to the loosening of the connection.

As is further indicated in the diagrammatic depiction of the singlefigure, the connecting counter-element 9 b can be connected here to areducing agent reservoir 12, which, e.g., is preferably a component of astationary or mobile desulfurization device 13, which is indicated inbroken lines in FIG. 1, via a hose line 10, by interposing a control andregulating device 11. This desulfurization device 13 can form, e.g., aservice point at a motor vehicle repair shop, in which during service ofthe motor vehicle, the connecting counter-element 9 b is connected tothe exhaust gas line connecting element 9 a in order to add a presetamount of reducing agent to regenerate the NO_(x) storage catalyst 5 inthe exhaust gas line 2 when the motor vehicle is parked, or the internalcombustion engine is idling, controlled or regulated as required by thecontrol and/or regulating device 11, for a preset time period. The addedreducing agent is preferably, as is the fuel, by means of which theinternal combustion engine 1 is operated, a low-sulfur mixture ofsubstances that has sulfur values of below 30 ppm.

As is further diagrammatically indicated in the single figure by theheating coil 14, the reducing agent of the desulfurization device 13 canalso be preheated to be fed or added in the heated state to the exhaustgas line 2.

Moreover, a component of the desulfurization device 13 can also be apumping device, by means of which it is ensured that the added reducingagent is added to the exhaust gas line at a specific pressure. In thisconnection, in particular in the area of the connecting element 9 a, anozzle device is preferably provided, by means of which a finedistribution of the added reducing agent into the exhaust gas line 2 ispossible.

In principle, corresponding communication devices would also make itpossible for this service point to communicate with the engine controlof the respective motor vehicle during the regeneration; suchcommunication would perform a “reset” subsequent to a successfulregeneration.

In addition, sensor data, such as, for example, temperature and/orlambda values, from the engine control device could also be used formonitoring or regulating.

1. A method for the addition of a reducing agent in an exhaust gas lineof an internal combustion engine of a motor vehicle, with at least oneNO_(x) storage catalyst that is arranged in the gas line of the internalcombustion engine, and with a metering device, by means of which apreset amount of a reducing agent is introduced into the exhaust gasline at preset times, wherein the metering device is created from astationary gas line connecting element that is made up of multiple partsat a defined position on the exhaust gas line and a connectingcounter-element that can be connected in a detachable manner to thisconnecting element and that can be arranged independently of the exhaustgas line and motor vehicle and in particular removed from the motorvehicle, in such a way that the connecting counter-element, for service,in particular when the motor vehicle is parked and/or the internalcombustion engine is idling, is connected to the exhaust gas lineconnecting element, and then, for purposes of regeneration of at leastone NO_(x) storage catalyst for a preset time, a preset amount ofreducing agent is introduced into the exhaust gas line, whereby afterthe regeneration, the connecting counter-element can again be detachedfrom the exhaust gas line connecting element.
 2. The method according toclaim 1, wherein the internal combustion engine is operated with a fuelwhose sulfur content is less than or equal to 30 ppm, in particular lessthan or equal to 10 ppm.
 3. The method according to claim 1, wherein thereducing agent is a mixture of substances with a sulfur content of lessthan or equal to 30 ppm, in particular less than or equal to 10 ppm. 4.The method according to one of claims 1, wherein the reducing agent isheated to a preset reducing agent temperature before the addition. 5.The method according to one of claims 1, wherein the regeneration speedof the internal combustion engine that is preset for service orregeneration is the idle speed of the internal combustion engine.
 6. Adevice for the addition of a reducing agent in an exhaust gas line of aninternal combustion engine of a motor vehicle, with at least one NO_(x)storage catalyst that is arranged in the exhaust gas line of theinternal combustion engine, and with a metering device, by means ofwhich at preset times, a preset amount of a reducing agent can beintroduced into the exhaust gas line, wherein the metering device iscreated from a stationary gas line connecting element that is made up ofmultiple parts at a defined position on the exhaust gas line and aconnecting counter-element that can be connected in a detachable mannerto this connecting element and that can be arranged independently of theexhaust gas line and motor vehicle, in particular removed from the motorvehicle.
 7. The device according to claim 6, wherein the connectingcounter-element is a component of a stationary or mobile desulfurizationdevice that is arranged at a service facility or an auto repair shop. 8.The device according to claim 6, wherein the connecting counter-elementand the exhaust gas line connecting element are connected to one anotherin a detachable manner with a quick-coupling connection that is designedto be gas-tight and/or liquid-tight when in the connected state.
 9. Thedevice according to claim 7, wherein the desulfurization device has areducing agent reservoir for a reducing agent as well as a controland/or regulating device for defined charging of the exhaust gas linewith a reducing agent.
 10. The device according to claim 9, wherein thedesulfurization device has a line connection, in particular a hose lineconnection, between the reducing agent reservoir and the connectingcounter-element, and wherein the control and/or regulating device iscoupled indirectly or directly into the hose line connection in the areabetween the connecting counter-element and the reducing agent reservoir.11. The device according to one of claims 7, wherein the desulfurizationdevice has a heating device by means of which the reducing agent can beheated to a preset temperature.
 12. The device according to one ofclaims 6 wherein the exhaust gas line connecting element is arranged inthe exhaust gas line in the area between a diesel particle filter and anNO_(x) storage catalyst.
 13. A method of desulferizing the catalyticconverter of a motor vehicle comprising: detachably connecting a fluidline to a portion of the exhaust gas line of said vehicle, between theengine and catalytic converter thereof, when said vehicle is located ata selected site; and introducing a sulfur reducing agent into saidexhaust gas line, through said fluid line.
 14. A method according toclaim 13 including operating said engine under a selected conditionduring introduction of said agent.
 15. A method according to claim 13including heating said reducing agent.
 16. A method according to claim13 including introducing said agent for a selected period of time.
 17. Asystem for desulferizing the catalytic converter of a motor vehiclecomprising: means for holding supply of a sulfur reducing agent at aselected site, provided with a line for dispensing said agent,detachably connectable to a portion of the exhaust gas line between theengine and the catalytic converter of a vehicle situated at saidselected site; and means for metering a supply of said agent throughsaid dispensing line.
 18. A system according to claim 17 including meansfor heating said agent.
 19. A system according to claim 17 wherein saiddispensing line and said portion of said exhaust gas line are providedwith fluid coupling members,